1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, and a computer program that process a digital image, and particularly to an image processing apparatus, an image processing method, and a computer program that process images of objects contained in an image taken by a digital camera.
More specifically, the present invention relates to an image processing apparatus, an image processing method, and a computer program that process pictures-in-picture information contained in a digital image, and particularly, to an image processing apparatus, an image processing method, and a computer program that extract, from a digital image containing a plurality of pictures-in-picture information items, each pictures-in-picture document by separation from a background image.
2. Description of Related Art
Recently, digital cameras are extensively used, which digitally encoded images taken by a solid-state imager, such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor) sensor. When compared with cameras with a silver salt film or a photosensitized plate, the digital cameras are advantageous in their capability of storing digitally encoded images into a memory so that the images be processed and managed by a computer, along with their being free from an issue of film's life time.
The digital cameras are usually used to take images of scenery and persons, but can also be used to digitize pictures-in-picture information. For example, pictures-in-picture information, such as documents including paper documents and business cards, a blackboard and a whiteboard whereon information is written for a presentation or a conference, or a screen image projected by a projector can be digitally inputted through a digital camera, for making it available for various image processing including, e.g., storage and management of information.
For example, an imaging apparatus having a business card capturing function has been proposed (see, e.g., Japanese Patent Application Publication No. JP 2003-283909). This imaging apparatus is configured to automatically zoom in on a business card to image the business card in almost the same size as the imaging angle of view.
Furthermore, an electronic camera has been proposed, which extracts textual information from an image signal obtained by imaging an object such as a business card or a signboard for conversion into a textual character string, and stores the textual information by classification on the basis of a predetermined item recognized from the textual character string (see, e.g., Japanese Patent Application Publication No. JP 2005-275447), whereby business card data can be easily managed without initial investment or cumbersome labor.
Furthermore, a digital image is split into foreground objects such as pictures in picture and a background, and only a pictures-in-picture region is extracted for use as a single photo image. The inventor of the present application calls “PicsInPic” the technology for extracting or exporting another photo image contained in a photo image.
In the related art, it has been typical practice to extract a contour of an image object such as a picture in picture on the basis of an edge image obtained by differential-processing a source image, to cut out the image object from a background image. For example, an image processing apparatus has been proposed, in which straight lines are detected from an edge image for imaging using Radon conversion, and a quadrilateral forming a contour for an imaging object is formed from the detected straight line parameters, for projective transformation to obtain an image which is formed as if the object for imaging were imaged from the front (see, e.g., Japanese Patent Application Publication No. JP 2005-275447).